At some point in the film we see Justine leaves her wedding and walks away to the garden of the villa,a man follows her ,she turns to him and have a sexual affair with him.The film director explained this scene as'The Empty Rituals of Reality'because Justine couldn't find herself in her own wedding.
The film director described Justine as 'a melancholic character by the grace of God',Justine is just like the planet melancholia ,she's striving to find her place in the world and believes that it's full of empty rituals like her wedding.
To Justine ,having sex is nothing more than an act of arbitrary which holds no more significance than holding someone's hand ,that's why she thinks infidelity isn't a bad thing after all.
Justine goes through a course of depression as the film progresses so claire (her sister) asks her to move in so that she could look after her ,she stays in bed all day and only gets up so her sister could feed her or bathe her.
Justine finally feels better when she learns about melancholia (a planet that will crush the earth),the film director explains this as follows Justine who always felt like a stranger on earth ,feels more home when she learns that the world is coming to an end'.
Claire is very different than her sister Justine,she's a sensible women who's unlike Justine eager to stay in the her world with her family.Through the whole film we see her panicking about melancholia and she only feels happy when she sees a slightest possibility the world isn't ending.
Before reaching the of the film where melancholia collides with earth, John,Clair's husband decides to commit suicide by taking some pills ,because he couldn't stand waiting for death anymore.
The film opens with a sum up of the whole plot,where we see we see the face of actress Kirsten Dunst as Justine,a seemingly depressed women we also see Claire carrying her child, a painting of a wintry hunting scene and a view of space.
Despite that Justine is person who had family issues that led her to being depressed,she's smart.On her wedding day,her employer mentioned how good she is at her job and he wanted to prompt her from copywriter to art director.
The film screen writer wanted to portray the single-minded characters in two personalities ,The business man who only thinks business and Justine and Claire's marriage who argued loudly during the wedding about how she's against the idea of marriage.
Compared to justine ,Micheal(Justine's groom) portrayed a very caring and understanding mate,he understood her mood swings during the wedding ,he took her into a room and showed a picture of a land with apple trees that he has bought for them and he made her promise to keep it but is didn't.
The planet melancholia is a metaphor for depression ,in the film melancholia the planet was a hidden planet that scientists discovered that it will crash the earth without anyone knowing,same goes with depression it's an emotional state that will hide for years then arrives and destroys everything.